Investigation on arc rotating characteristics of a micro-cathode arc thruster

Micro-cathode arc thruster (μCAT) has the advantages of super lightweight, high specific impulse and modularity, which has a broad application prospect in micro satellites and nanosats. However, from the engineering aspect, the lifetime is the key issue that determines the space flight applications for μCAT. The arc rotating characteristics of the μCAT play an important role in influencing the lifetime and ablation of the conductive film. In this paper, we propose a magnetic probe array to measure the azimuthal varying magnetic field components from the discharge arc, and thus to evaluate the arc rotating characteristics of the thruster. The design of the magnetic probe is carried out based on Faraday's law of electromagnetic induction and the exit dimensions of the thruster. A capacitive discharge in the energised straight conductor is used as a standard magnetic field for the magnetic probe calibration. The average calibration coefficient is calculated to be 0.311 T/V, with the maximum repeatability error of 8.9 %. Through multi-points magnetic field measurements, the arc rotation speed, angle, duration, and the change rate of the arc rotation speed can be investigated experimentally. By changing the discharge energy levels, it is measured that the tendency of arc rotation slowing down during the discharge process become smoother from 17.65 % to 13.91 % with the decrease of the μCAT discharge energy. With the increase of the applied magnetic field, it is found that the rotation angle of the μCAT discharge arc is significantly increased around 300°, while the discharge time is reduced to a limited extent by 14.11 μs. Furthermore, the new insights into arc behavior can provide valuable perspectives on issues related to overall performance of the thruster.